It is good to have a single main objective, that catches the imagination, and that it is clear whether someone has won or not.

However, it is worth also handing out smaller sums on a discretionary basis (perhaps annually) for the best contribution that progresses that state of the art towards meeting the main objective? If so, what might such milestones be in the case of a Universal Constructor?

Or, secondly, one could reward reaching the 90% independence mark for particular sub-systems.

So that might be:

5 % of the current prize total for a system that can 90% self-replicate

5 % of the current prize total for a system that can 90% self-assemble

a further 10 % of the current prize total for a system that can both 90% self-replicate AND can 90% replicate a system that can 90% self-assemble

a further 10 % of the current prize total for a system that can both 90% self-assemble AND can 90% assemble a system that can 90% self-replicate

the final 70 % of the current prize total for a system that meets the full criteria (or rather, 100% of the already unclaimed prize total)

Your thoughts? What would motivate you? How do those objectives compare in difficulty? What about a partial success, which the following year is then refined and successfully submitted by someone else? Would an 'all or nothing' approach encourage secrecy rather than mutual cooperation and incremental improvement?